Activists on both sides of the debate over same-sex marriage are saying “I do” this week to rallies and other demonstrations that coincide with oral arguments in two pivotal Supreme Court cases.

Justices on Tuesday and Wednesday will hear challenges to California’s Proposition 8, which outlawed same-sex marriage in the state, and to a section of the federal Defense of Marriage Act, which defined marriage as between a man and a woman. The decisions, expected in June, have the potential to allow gay and lesbian couples to marry across the U.S.

United for Marriage: Light the Way to Justice, a coalition of groups that support marriage equality, will hold a rally on Tuesday morning in the plaza in front of the Supreme Court, with participants encouraged to wear red, symbolizing love. Other such events will take place across the country, including vigils nationwide Monday evening.

More than 175 events in all 50 states are planned, Human Rights Campaign spokesman Kevin Nix said.

At the Supreme Court plaza rally Tuesday, proponents of same-sex marriage will include Baltimore Ravens linebacker Brendon Ayanbadejo, civil rights and religious leaders, and a number of Republicans including David Frum, a former speechwriter for President George W. Bush.

“More people are motivated than I’ve ever seen before to show up in Washington, D.C., to show the human face behind these historic cases,” Stuart Gaffney of Marriage Equality USA said.

Gaffney said he is in town from San Francisco for the week’s events. “Decades of activism have been leading up to this moment, and these two cases feel like the culmination of almost a lifetime of activism,” he added.

Most of the organizers and participants in these demonstrations say they are not looking to sway the opinion of the nine justices as much as they are continuing their ongoing grass-roots push for support from ordinary Americans in the court of public opinion.

“I don’t think it’s about influencing the court’s decision; it’s about being a moral witness to ending marriage discrimination,” said Evan Wolfson, founder and president of the Freedom to Marry campaign. “These cases are part of a broader strategy that has brought us to this moment and will carry us to victory whether in June or as soon thereafter as possible.”

Public opinion polls show increasing support for gay marriage, and more political candidates and elected officials have voiced their approval for same-sex marriages in the weeks leading up to this week’s arguments. Sen. Rob Portman, R-Ohio, last week said he’s a supporter and announced he has a gay son. Former Secretary of State Hillary Rodham Clinton and President Bill Clinton, who signed DOMA into law, have both voiced their approval for same-sex marriage. Sen. Claire McCaskill, D-Mo., announced her support over the weekend, followed by Sen. Mark Warner, D-Va., who announced his conversion on Facebook on Monday.

Democratic lobbyist Steve Elmendorf, whose clients at Elmendorf Ryan include the Human Rights Campaign, said the position on same-sex marriages “is becoming more and more the central question elected officials are going to have to answer.” He added that no serious contender for the Democratic presidential ticket in 2016 could oppose marriage equality.

And “more and more, it will be a litmus test for members and senators seeking support,” he said. “The voices against it are small and few.”

But organizers behind the March for Marriage, a demonstration in opposition to same-sex marriage, say they expect thousands of supporters to show up on the National Mall on Tuesday. Groups such as Focus on the Family and the Family Research Council are participating in the march, spearheaded by the National Organization for Marriage.

“We’re calling on the Supreme Court to respect the rights of over 45 million Americans who have voted to protect marriage in their state constitutions,” said Thomas Peters, a spokesman for the National Organization for Marriage.

The demonstrators against gay marriage will convene Tuesday morning on the Mall, then march to the Supreme Court and return back to the Mall for a rally, Peters said.

Tom McClusky, senior vice president of government affairs for the Family Research Council, said that in addition to his group’s involvement with the March for Marriage, his organization has been pressing its side with members of Congress and their aides and with religious leaders as part of its Stand for Marriage campaign.

As for the cases, McClusky noted that with the rally, he isn’t exactly calling on activists to lobby the Supreme Court. “We do ask them to pray, of course,” he said.